libmount: add reference counting to libmount_fs

 * mnt_new_fs() returns object with refcount=1
 * mnt_free_fs() does not care about reference counter

 * new functions mnt_ref_fs() and mnt_unref_fs()

 * mnt_table_add_fs() and mnt_table_rem_fs() uses reference counter

 * libmmnt_context uses reference counter for internal FS (as it could be
   shared outside the context)

 * backwardly incompatible change:

	- FS could be deallocated after mnt_table_remove_fs()

 * it's recommended to use mnt_unref_fs() after mnt_table_add_fs()

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 10 insertions, 7 deletions

diff --git a/libmount/src/tab_update.c b/libmount/src/tab_update.c
index 9603f77ec..b5c92726f 100644
--- a/libmount/src/tab_update.c
+++ b/libmount/src/tab_update.c
@@ -70,7 +70,7 @@ void mnt_free_update(struct libmnt_update *upd)
 
 	DBG(UPDATE, mnt_debug_h(upd, "free"));
 
-	mnt_free_fs(upd->fs);
+	mnt_unref_fs(upd->fs);
 	mnt_free_table(upd->mountinfo);
 	free(upd->target);
 	free(upd->filename);
@@ -180,7 +180,7 @@ int mnt_update_set_fs(struct libmnt_update *upd, unsigned long mountflags,
 		DBG(UPDATE, mnt_fs_print_debug(fs, stderr));
 	}
 
-	mnt_free_fs(upd->fs);
+	mnt_unref_fs(upd->fs);
 	free(upd->target);
 	upd->ready = FALSE;
 	upd->fs = NULL;
@@ -350,7 +350,7 @@ static int utab_new_entry(struct libmnt_update *upd, struct libmnt_fs *fs,
 	return 0;
 err:
 	free(u);
-	mnt_free_fs(upd->fs);
+	mnt_unref_fs(upd->fs);
 	upd->fs = NULL;
 	return rc;
 }
@@ -671,6 +671,8 @@ static int add_file_entry(struct libmnt_table *tb, struct libmnt_update *upd)
 		return -ENOMEM;
 
 	mnt_table_add_fs(tb, fs);
+	mnt_unref_fs(fs);
+
 	return update_table(upd, tb);
 }
 
@@ -722,7 +724,6 @@ static int update_remove_entry(struct libmnt_update *upd, struct libmnt_lock *lc
 		if (rem) {
 			mnt_table_remove_fs(tb, rem);
 			rc = update_table(upd, tb);
-			mnt_free_fs(rem);
 		}
 	}
 	if (lc)
@@ -905,7 +906,7 @@ static int test_add(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_fs_set_options(fs, argv[4]);
 
 	rc = update(NULL, fs, 0);
-	mnt_free_fs(fs);
+	mnt_unref_fs(fs);
 	return rc;
 }
 
@@ -928,7 +929,7 @@ static int test_move(struct libmnt_test *ts, int argc, char *argv[])
 
 	rc = update(NULL, fs, MS_MOVE);
 
-	mnt_free_fs(fs);
+	mnt_unref_fs(fs);
 	return rc;
 }
 
@@ -943,7 +944,7 @@ static int test_remount(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_fs_set_options(fs, argv[2]);
 
 	rc = update(NULL, fs, MS_REMOUNT);
-	mnt_free_fs(fs);
+	mnt_unref_fs(fs);
 	return rc;
 }
 
@@ -962,7 +963,9 @@ static int test_replace(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_fs_set_source(fs, argv[1]);
 	mnt_fs_set_target(fs, argv[2]);
 	mnt_fs_append_comment(fs, "# this is new filesystem\n");
+
 	mnt_table_add_fs(tb, fs);
+	mnt_unref_fs(fs);
 
 	rc = mnt_table_replace_file(tb, mnt_get_fstab_path());
 	mnt_free_table(tb);